New Delhi: The national capital was on Tuesday brought under an elaborate ground-to-air security apparatus on the eve of Independence Day celebrations to pre-empt any terror strike.

Thousands of Delhi Police and paramilitary personnel were deployed in and around the city, especially near the Red Fort from where Prime Minister Manmohan Singh will unfurl the tricolour and address the nation.

Around 50 CCTVs will be installed in and around the Red Fort to ensure incident-free celebrations while sharpshooters of the NSG will be deployed on the high-rises near the 17th century Mughal monument, officials said.

Security agencies are constantly reviewing arrangements at the Red Fort and have zeroed in on the 'safe houses' where the Prime Minister and other leaders should be taken to in case of a terrorist strike, they said.

According to the officials, the localities around Red Fort have been sanitised and informers have been deployed to keep a check on any movement of anti-national elements.

Specialised units like Quick Reaction Teams, SWAT and Vajra are being deployed. An intense vigil will also be maintained on key installations like Parliament complex, international airport, railway stations, inter-state bus terminals and Metro stations.

Besides patrolling of the skies by helicopters, an air defence mechanism will also be put in place around the venue to thwart any terror attacks. Delhi Police has also intensified checking at all the border points, the officials said.

Police have also asked operators of guest-houses, cyber cafes, telephone booths and taxi services to keep a watch on their customers and report about suspicious people.

While owners of guest-houses and cyber cafes have been asked to install CCTVs, telephone booth operators were instructed to keep separate registers of those making local, STD and ISD calls, the officials said.

Owners of guest houses and hotels will also be asked not to allow their guests to use hotel address for getting a mobile connection, they said.